Optical arrangement and projection exposure system for microlithography with passive thermal compensation

ABSTRACT

An optical arrangement with a light source includes an optical element that is fastened in a mount. The light source emits radiation and the optical element is acted on thereby such that the heat that results lacks symmetry corresponding to the shape of the optical element. A connecting structure is provided between the optical element and the mount and has a symmetry that does not correspond to the shape of the optical element and effects an at least partial homogenization of the temperature distribution in the optical element.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a Continuation of patent application Ser. No.09/934,817 filed Aug. 21, 2001, of the same inventors, the priority ofwhich under 35 USC 120 is claimed for this application.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] This invention relates to an optical arrangement with a lightsource and an optical element, and more particularly to projectionexposure systems for microlithography, in which a thermal effect that isnot rotationally symmetrical that results from the irradiation from thelight source is compensated. Microlithography notoriously is the art ofproducing structures in the micrometer and submicrometer range—interalia for microelectronic devices—by photolithography.

[0005] This situation is of particular importance in wafer scanners witha slit-shaped image field: either a narrow rectangle slit with a widthto length ratio of e.g. typically 1:5 to 1:9, or an arcuate shape,particularly in mirror systems.

[0006] 2. Discussion of Relevant Art

[0007] Active compensation of the imaging errors resulting fromasymmetric thermal effects is known from European Patent EP-A 0 678 768,and its counterpart U.S. Pat. No. 5,805,273 to Unno by regulated orcontrolled non-rotationally-symmetrical heating or cooling and also, byway of a suggestion, by mechanical stressing.

[0008] The like was described earlier in European Patent EP-B1 0 532236, preferably as heating for mirrors.

SUMMARY OF THE INVENTION

[0009] The invention has as its object to markedly reduce or rendersymmetrical, by the simplest possible means, the change of theproperties of optical elements due to light absorption and the resultingheating, particularly in projection exposure systems.

[0010] This object is achieved by an optical arrangement and byprojection exposure systems having an optical arrangement with thefollowing features:

[0011] An optical arrangement with a light source, that emits radiation,having a mount, and an optical element fastened in the mount. Theoptical element, is acted on by the radiation such that heat resultsfrom the radiation that lacks symmetry corresponding to the shape of theoptical element. A connecting structure between the optical element andthe mount has a symmetry that does not correspond to the shape of theoptical element and effects an at least partial homogenization oftemperature distribution in the optical element.

[0012] Active, controlled or regulated operations on the opticalelements are dispensed with. The total energy input into the arrangementis reduced by the avoidance of active elements and particularly of aheating system.

[0013] On the other hand, the invention with asymmetrical coolingdeparts from the proven constructional principles of mountings with highsymmetry, which principles particularly for projection exposure systemshave heretofore been driven to the utmost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention will be described in more detail hereinbelow withreference to the accompanying drawings, in which

[0015]FIG. 1 shows schematically a lens with a slit-shaped illuminationand tab connections of different materials;

[0016]FIG. 2 shows schematically a lens with dipole-like illuminationand connections to the mounting, of different cross sections;

[0017]FIG. 3a shows schematically a lens with a slit-shaped illuminationin a symmetrical mounting with a cooling body ofnon-rotationally-symmetrical shape;

[0018]FIG. 3b shows a section along section line IIIb-IIIb of FIG. 3a;

[0019]FIG. 3c shows a section along section line IIIc-IIIc FIG. 3a;

[0020]FIG. 4 shows schematically in cross section a variant with acooling tab and heat conducting cable;

[0021]FIG. 5a shows a FEM model with symmetrically arranged like coolingbodies;

[0022]FIG. 5b shows schematically in cross section another variant witha cooling tab and heat conducting cable;

[0023]FIG. 6 shows a FEM model similar to FIG. 5a, but with the coolingbody varied in position, size and material;

[0024]FIG. 7 shows a variant with a cooling body withtemperature-induced variation of the cooling effect;

[0025]FIG. 8 shows, in schematic section, a mirror with differentcooling effected by webs of different materials; and

[0026]FIG. 9 shows schematically a general view of a projection exposuresystem.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0027] The arrangement of FIG. 1 shows a lens mount 2 in which a lens 1is held as free as possible from stress and fixed exactly in position,by numerous webs 21-28 (eight are shown). The webs 21-28 (spokes, tabs)are adhered to the edge of the lens, or connected by other jointingmethods.

[0028] The lens 1 is illuminated in a slit-shaped cross section 10. Theproblem in just those projection exposure systems that operate in theVUV (vacuum ultraviolet) and DUV (deep ultraviolet) region is that thelens materials have a considerable absorption, and consequently there isa considerable supply of heat into the cross section 10. The relatedrise in temperature brings about a change of the refractive index, andin addition a deformation due to thermal expansion. The overall resultis a change of the lens operation, with astigmatic operation.

[0029] Cooling takes place to only a small extent by means of thesurrounding gas (usually helium in projection exposure systems) and bythermal radiation. The heat is transferred to the mount 2 primarily viathe lens body 1, the joint spot (adhesive), and the gas in thesurroundings of the joint spot, and the webs 21-28.

[0030] According to the invention, the webs 21-28 in this embodiment areconstituted of different materials, so that they have different thermalconductivities. For example, the webs 21, 25 next to the slit-shapedcross section 10 are of silver, with very good thermal conductivity;those furthest away 23, 27 are of lead, with a low thermal conductivity,and the webs in between 22, 24, 26, 28 are of aluminum with mediumthermal conductivity. The temperature distribution in the lens 1 is thusrelatively lowered between the webs 21, 23, and relatively raisedbetween the webs 23, 25, whereby there result a homogenization andsymmetrization of the temperature distribution and a reduced disturbanceof the optical properties of the lens 1.

[0031] In practice, further properties of the materials used, such astheir strength, elasticity, and thermal expansion are to be considered.Simulation calculations for the mechanical, thermal and opticalproperties, using the Finite Element Method, make possible an optimizedselection and embodiment of the arrangement.

[0032] An alternative, which however is also suitable for combinationwith the above described embodiment, is shown in FIG. 2. Here the lens 1and mount 2 are connected by means of webs 211-214 (for clarity, onlyfour are shown; in practice there are more) with different crosssections and thus different thermal conduction. Different mechanicalproperties are prevented by means of each web 211-214 having similarspring joints 221-224. The thermal conduction over the adjacentlysituated narrow gaps (only minimal mobility of the joints is required)takes place sufficiently effectively by means of the filling gas(helium) or by a flexible metal cable (stranded conductor) (see FIG.6b).

[0033] The exact combination is established here also with the supportof simulation calculations. A combination with the use of differentmaterials as shown in FIG. 1 opens up wider possibilities of matching.

[0034] Additionally, a “dipole” illumination of the lens with twoeccentric light spots 101, 102 is shown in this FIG. 2, as occurs in theregion of the diaphragm plane and equivalent planes of projectionexposure systems with symmetrical oblique illumination. Astigmaticerrors due to light absorption also arise therewith, and can be reducedby passive compensating cooling.

[0035]FIGS. 3a-3 c show a variant of the invention with an additionalthermally conducting element 3, which is provided only for theequalizing cooling.

[0036] The lens 1 and mount 2 are in this case connected with uniformwebs or with selectively cooling webs according to FIG. 1 or 2. Anyother mounting technique is likewise usable.

[0037] The thermally conducting element 3 is connected fast to the mount2 with good thermal conduction, and covers portions of the lens 1through which no light passes and which are thus outside the illuminatedsurface 10, also shown here as a slit.

[0038] This covering is preferably free from contact, at a spacing ofabout 0.1 mm, so that a good thermal transfer is assured by means of thefilling gas, but no stresses can be transmitted into the lens 1. Betterthermal conduction of course results when the gap between the lens 1 andthe thermally conducting element 3 is filled with adhesive, a gel,liquid crystals, or the like material which transmits as little stressas possible.

[0039] The thermal conduction and its local distribution is set by theshape of the thermally conducting part 3; FIG. 3b shows how the part 3extends to the neighborhood of the illuminated region 10 in thedirection A-A of the length of the slit, and FIG. 3c shows that thedistance is kept large in the transverse direction B-B.

[0040] With the embodiment shown in FIG. 3a of the thermally conductingelement 3, with numerous fingers or spokes, their width, shape, anddistribution can be made use of for the adjustment of the thermalconduction. In an embodiment as an unbroken disk or as a perforateddiaphragm, the thickness of the thermally conducting element can belocally different. It is also possible to make the individual fingers,analogously to the webs 21-28 of FIG. 1, of different thermallyconducting materials. The thermally conducting element 3 can of coursealso be arranged on both sides of the lens 1.

[0041]FIG. 4 shows, in an illustration corresponding to FIG. 3b, amanner in which the cooling element 3 can be brought into materialcontact or shape-fitting contact with the lens 1 without impairing themechanical properties of the mount 2 and the connecting portions 21. Forthis purpose, the cooling element 3 is provided with a flexible,heat-conducting cable 30—e.g., a stranded copper wire—and is connectedto a heat sink 20.

[0042]FIG. 5a shows in plain view the finite element model of a quadrantof a lens 1 of quartz glass (middle thickness 14.4 mm, upper radius ofcurvature 1600 mm, lower radius of curvature 220 mm, biconvex, diameter160 mm). Eight solid tabs (51, 52, 53) of aluminum are uniformlydistributed, arranged on the lens 1 in the manner which will be apparentfrom the cross section, FIG. 5b. They are 30 mm wide, 2 mm thick abovethe lens and covering it for 6 mm radially, outside which they are afurther 8 mm long radially, with a thickness of 4 mm. At the outer edge,they are kept to the base temperature by flexible, thermally conductivestranded wires 50, for example.

[0043] The displayed surface of the lens 1 is exposed to an introductionof 1 W/cm² of heat by light absorption in the region 4, whichapproximates to about a right angle in the selected element division.The temperature increase in the middle point then reaches 7.6milli-degrees. The isotherms 0.1-0.9 are shown drawn in and indicate thecourse of the lines with the corresponding fraction of this temperatureincrease. With a higher introduction of heat, the temperature increaseis linearly scaled over a wide range.

[0044] It is quite evident that in this embodiment with a symmetricalcooling arrangement, the temperature distribution which is obtained isdistributed with marked asymmetry over the whole lens.

[0045] In the embodiment according to the invention, which is shown inFIG. 6, the cooling tabs situated on the Y-axis are omitted. The coolingtabs 510 situated on the X-axis are doubled in width and in addition aremade of silver, which conducts heat better. The tabs 52 between remainunaltered, as likewise the heat supply in the region 4.

[0046] The temperature increase at the middle point now becomes 9.2milli-degrees. The isotherms now show good rotational symmetry up toabout 0.7 times the maximum temperature increase and to half the lensdiameter.

[0047] The mechanical mounting of the lens 1 can either take place bymeans of the cooling tabs 510, 52, or an optional mounting technique isprovided which preferably has comparatively small thermal conduction.

[0048]FIG. 7 shows a variant, similar to FIGS. 3a-c, in which thefingers 31, 32 of the thermally conducting element are constituted ofbimetal—two layers of material of different thermal expansion. To theleft in the Figure, the bimetal strip 31 is bent away from the lens 1 atthe low temperature t₁, and can take up only little heat. To the rightin the Figure, the bimetal strip 32 is straight at the highertemperature T₂ and is situated at a small spacing from the lens 1, sothat it can carry away much heat.

[0049] The invention can of course also be applied to prismatic parts,gratings, or mirrors, and likewise to all optical components subject touneven heat loading, in addition to the lenses as shown in the foregoingembodiments.

[0050]FIG. 8 shows an embodiment specially adapted to a mirror 6. Themirror 6 is supported on a mounting 7 by means of supports 71-77, whichare individual webs or support rings, distributed on its back side.

[0051] The cooling action is adjusted according to requirements, tomatch the illuminated surface 10, by the distribution of the supports71-77 on the back side of the mirror 6, by their shape, and also bymeans of the specific thermal conductivity of their material (e.g.,silver at the middle 74, lead 72, 76 at the edges 72, 76, and otherwise(73, 75) aluminum, and the outer edge 71, 77 of glass ceramics).

[0052] The different thermal expansion of the materials for the supports71-77 can be used if necessary in order to compensate for deformationsof the mirror 6 due to heating, or else to cause them in a targetedmanner. In the latter case, disturbances of other optical elements whichcooperate in a system with the mirror 6 can be compensated.

[0053]FIG. 9 shows, in a schematic overview, the complete optical systemof a projection exposure system for microlithography. A DUV excimerlaser serves as the light source 61. A beam-forming optics 62 with zoomaxicon objective 63 an optional diaphragm 64 (e.g. variable,conventional, ring aperture, dipole aperture, quadrupole aperture) and ahomogenizing quartz rod 65 illuminates the REMA diaphragm 66, which isimaged by the following REMA objective 67 as a sharp-edged homogeneouslight spot, in particular as a narrow scanning slit, on the mask 68.

[0054] The following reducing projection objective 69 images the mask 68onto the wafer 70. The lenses 671 and 672 of the REMA objective 67 and692 of the projection objective 69 are situated in near field planes andtherefore are now preferred optical elements on which the coolingaccording to the invention is used. This cooling reduces the imagingerrors arising due to the narrow slit-shaped illuminated field in ascanner in which the mask 68 and wafer 70 are synchronously scanned.

[0055] The lens 691 is arranged nearest the aperture diaphragm 690 ofthe projection objective 69. It is specially strained by special kindsof illumination, for example, a dipole aperture (see FIG. 2). However,this disturbance can also be reduced by the asymmetric cooling accordingto the invention.

[0056] It is clear that the description of the Figures only describesexamples for the invention. In particular, multifarious combinations ofthe described features are possible according to the invention, and thecooling can be adjustably embodied, in order to adjust, to adapt tochanges, and so on.

We claim:
 1. An optical arrangement, comprising: a light source thatemits radiation, a mount, an optical element fastened in said mount,wherein said optical element is acted on by said radiation such that aheat supply results from said radiation that lacks symmetrycorresponding to the shape of said optical element, and a connectingstructure between said optical element and said mount, having a symmetrycharacteristic that does not correspond to the shape of the opticalelement.
 2. An optical arrangement, comprising: a light source thatemits radiation, a mount, an optical element fastened in said mount,wherein said optical element is acted on by said radiation such thatheat that results from said radiation lacks symmetry corresponding tothe shape of said optical element, and a single- or multi-part thermallyconducting element arranged in operative connection with said opticalelement and said mount and having a form of heat transport that effectsan at least partial compensation of the asymmetry of temperaturedistribution in said optical element.
 3. A projection exposure systemfor microlithography, comprising: an optical element that is heated byradiation in a manner that lacks rotational symmetry, and a coolingsystem for said optical element that lacks rotational symmetry, saidcooling system including passive thermally conducting devices thateffect cooling.
 4. A projection exposure system for microlithography,comprising an optical element that is heated by radiation in a mannerthat lacks rotational symmetry, and at least one passively thermallyconducting part arranged in thermal contact with said optical element,which part covers a portion of the cross section of said optical elementwhich is not exposed to said radiation, and which part reducestemperature gradients in said optical element.
 5. The opticalarrangement according to claim 1, in which said optical elementcomprises a transmitting element.
 6. The optical arrangement accordingto claim 5, in which said transmitting element comprises a lens.
 7. Theoptical arrangement according to claim 2, in which said optical elementcomprises a transmitting element.
 8. The optical arrangement accordingto claim 7, in which said transmitting element comprises a lens.
 9. Theprojection exposure system according to claim 3, in which said opticalelement comprises a transmitting element.
 10. The projection exposuresystem according to claim 9, in which said transmitting elementcomprises a lens.
 11. The projection exposure system according to claim4, in which said optical element comprises a transmitting element. 12.The projection exposure system according to claim 11, in which saidtransmitting element comprises a lens.
 13. The optical arrangementaccording to claim 1, in which said optical element comprises a mirror.14. The optical arrangement according to claim 2, in which said opticalelement comprises a mirror.
 15. The projection exposure system accordingto claim 3, in which said optical element comprises a mirror.
 16. Theprojection exposure system according to claim 4, in which said opticalelement comprises a mirror.
 17. The optical arrangement according toclaim 1, having a slit-shaped image field.
 18. The optical arrangementaccording to claim 2, having a slit-shaped image field.
 19. Theprojection exposure system according to claim 3, having a slit-shapedimage field.
 20. The projection exposure system according to claim 4,having a slit-shaped image field.
 21. The optical arrangement accordingto claim 5, in which said optical element is arranged near a fieldplane.
 22. The optical arrangement according to claim 7, in which saidoptical element is arranged near a field plane.
 23. The projectionexposure system according to claim 9, in which said optical element isarranged near a field plane.
 24. The projection exposure systemaccording to claim 11, in which said optical element is arranged near afield plane.
 25. The optical arrangement according to claim 1, furthercomprising a reticle, the illumination of which lacks rotationalsymmetry.
 26. The optical arrangement according to claim 25, in whichsaid reticle illumination consists of off-axis, dipole or quadrupoleillumination type.
 27. The optical arrangement according to claim 2,further comprising a reticle, the illumination of which lacks rotationalsymmetry.
 28. The optical arrangement according to claim 27, in whichsaid reticle illumination consists of off-axis, dipole or quadrupoleillumination type.
 29. The projection exposure system according claim 3,further comprising a reticle, the illumination of which lacks rotationalsymmetry.
 30. The projection exposure system according to claim 29, inwhich said reticle illumination consists of off-axis, dipole orquadrupole illumination type.
 31. The projection exposure systemaccording to claim 29, in which said optical element is arranged near apupil plane.
 32. The projection exposure system according to claim 4,further comprising a reticle, the illumination of which lacks rotationalsymmetry.
 33. The projection exposure system according to claim 32, inwhich said reticle illumination consists of off-axis, dipole orquadrupole illumination type.
 34. The projection exposure systemaccording to claim 32, in which said optical element is arranged near apupil plane.
 35. The optical arrangement according to claim 1, in whichsaid connecting structure comprises portions of different materials. 36.An optical arrangement comprising: a light source that emits radiation,a mount, an optical element fastened to said mount, wherein said opticalelement is acted on by said radiation such that heat that results fromsaid radiation lacks symmetry corresponding to the shape of said opticalelement, and a single- or multi-part passive thermally conductingelement arranged in operative connection with said optical element andsaid mount and having a form of heat transport that effects an at leastpartial compensation of the asymmetry of temperature distribution insaid optical element, wherein said passive thermally conducting elementcomprises an assembly of portions of different material.
 37. Aprojection exposure system for microlithography, comprising: an opticalelement that is heated by radiation in a manner that lacks rotationalsymmetry, and a cooling system for said optical element that lacksrotational symmetry, said cooling system including passive thermallyconducting devices that effect cooling, wherein said passive thermallyconducting devices comprise portions of different material.
 38. Theprojection exposure system according to claim 4, in which said at leastone part of a thermal conductor in thermal contact with said opticalelement comprises a plurality of different materials.
 39. The opticalarrangement according to claim 1, in which said connecting structurecomprises adjustable portions.
 40. The optical arrangement according toclaim 2, in which said thermally conducting element is adjustable. 41.The projection exposure system according to claim 3, in which saidthermally conducting elements comprise adjustable portions.
 42. Theprojection exposure system according to claim 4, in which said at leastone part of a thermal conductor in thermal contact with said opticalelement is at least partially adjustable.
 43. An optical arrangement,comprising: a light source, at least one optical element, and a passivecompensator of thermal effects caused by radiation from said lightsource, which compensator lacks rotational symmetry.
 44. A projectionexposure system for microlithography, comprising: an optical elementthat is heated by radiation in a manner that lacks rotational symmetry,and a cooling system that lacks rotational symmetry for said opticalelement, said cooling system comprising passive thermally conductingdevices.
 45. An optical arrangement, comprising: a light source thatemits radiation, a mount, an optical element fastened in said mount,wherein said optical element is acted on by said radiation such that aheat supply results from said radiation that lacks symmetrycorresponding to the shape of said optical element, and a connectingstructure between said mount and said optical element, having a symmetrycharacteristic that substantially does not correspond to the shape ofthe optical element.
 46. An optical arrangement, comprising: a lightsource that emits radiation, a mount, an optical element fastened insaid mount, wherein said optical element is acted on by said radiationsuch that heat that results from said radiation lacks symmetrycorresponding to the shape of said optical element, and a single- ormulti-part thermally conducting element arranged in operative connectionwith said optical element and said mount and having a form of heattransport that effects an at least partial compensation of the asymmetryof temperature distribution in said optical element.
 47. A projectionexposure system for microlithography, comprising: an optical elementthat is heated by radiation in a manner that lacks rotational symmetry,and a cooling system for said optical element that lacks rotationalsymmetry, said cooling system including passive thermally conductingelements that effect cooling, in which said thermally conductingelements comprise adjustable portions.
 48. A projection exposure systemfor microlithography, comprising an optical element that is heated byradiation in a manner that lacks rotational symmetry, and at least onepassive thermally conducting part arranged in thermal contact with saidoptical element, which part covers a portion of the cross section ofsaid optical element which is not exposed to said radiation, and whichpart reduces temperature gradients in said optical element, in whichsaid at least one passive thermally conducting part of a thermalconductor in thermal contact with said optical element comprises aplurality of different materials and in which said at least one passivethermally conducting part of a thermal conductor in thermal contact withsaid optical element is at least partially adjustable.
 49. The opticalarrangement according to claim 80, in which said optical elementcomprises a transmitting element.
 50. The optical arrangement accordingto claim 49, in which said transmitting element comprises a lens. 51.The optical arrangement according to claim 88, in which said opticalelement comprises a transmitting element.
 52. The optical arrangementaccording to claim 51, in which said transmitting element comprises alens.
 53. The projection exposure system according to claim 48, in whichsaid optical element comprises a transmitting element.
 54. Theprojection exposure system according to claim 53, in which saidtransmitting element comprises a lens.
 55. The projection exposuresystem according to claim 84, in which said optical element comprises atransmitting element.
 56. The projection exposure system according toclaim 55, in which said transmitting element comprises a lens.
 57. Theoptical arrangement according to claim 80, in which said optical elementcomprises a mirror.
 58. The optical arrangement according to claim 88,in which said optical element comprises a mirror.
 59. The projectionexposure system according to claim 48, in which said optical elementcomprises a mirror.
 60. The projection exposure system according toclaim 84, in which said optical element comprises a mirror.
 61. Theoptical arrangement according to claim 80, having a slit-shaped imagefield.
 62. The optical arrangement according to claim 88, having aslit-shaped image field.
 63. The projection exposure system according toclaim 48, having a slit-shaped image field.
 64. The projection exposuresystem according to claim 84, having a slit-shaped image field.
 65. Theoptical arrangement according to claim 80, in which said optical elementis arranged near a field plane.
 66. The optical arrangement according toclaim 65, in which said optical element is arranged near a field plane.67. The projection exposure system according to claim 48, in which saidoptical element is arranged near a field plane.
 68. The projectionexposure system according to claim 84, in which said optical element isarranged near a field plane.
 69. The optical arrangement according toclaim 80, further comprising a reticle, the illumination of which lacksrotational symmetry.
 70. The optical arrangement according to claim 69,in which said reticle illumination consists of off-axis, dipole orquadrupole illumination.
 71. The optical arrangement according to claim88, further comprising a reticle, the illumination of which lacksrotational symmetry.
 72. The optical arrangement according to claim 71,in which said reticle illumination consists of off-axis, dipole orquadrupole illumination type.
 73. The projection exposure systemaccording claim 48, further comprising a reticle, the illumination ofwhich lacks rotational symmetry.
 74. The projection exposure systemaccording to claim 73, in which said reticle illumination consists ofoff-axis, dipole or quadrupole illumination type.
 75. The projectionexposure system according to claim 48, in which said optical element isarranged near a pupil plane.
 76. The projection exposure systemaccording to claim 84, further comprising a reticle, the illumination ofwhich lacks rotational symmetry.
 77. The projection exposure systemaccording to claim 76, in which said reticle illumination consists ofoff-axis, dipole or quadrupole illumination type.
 78. The projectionexposure system according to claim 84, in which said optical element isarranged near a pupil plane.
 79. The optical arrangement according toclaim 88, in which said connecting structure comprises portions ofdifferent materials.
 80. An optical arrangement comprising: a lightsource that emits radiation, a mount, an optical element fastened tosaid mount, wherein said optical element is acted on by said radiationsuch that heat that results from said radiation lacks symmetrycorresponding to the shape of said optical element, and a single- ormulti-part passive thermally conducting element arranged in operativeconnection with said optical element and said mount and having a form ofheat transport that effects an at least partial compensation of theasymmetry of temperature distribution in said optical element, whereinsaid passive thermally conducting element comprises an assembly ofportions of different material.
 81. The optical arrangement according toclaim 80, in which said connecting structure comprises adjustableportions.
 82. The optical arrangement according to claim 84, in whichsaid thermally conducting element is adjustable.
 83. The projectionexposure system according to claim 84, in which said thermallyconducting elements comprise adjustable portions.
 84. A projectionexposure system comprising: an optical element that is heated byradiation in a manner that lacks rotational symmetry, and a coolingsystem for said optical element that lacks rotational symmetry, saidcooling system including passive thermally conducting devices thateffect cooling, wherein said passive thermally conducting devicescomprise portions of different material.
 85. A reflective mirror for usein an optical system, the mirror comprising a mirror body defining amirror surface, an illuminated region of the mirror surface, and atleast one thermally conducting element attached to the mirror outsidethe illuminated region, the thermally conducting element havingflexibility and forming a heat conducting connection away from themirror.
 86. The reflective mirror according to claim 85, wherein thethermally conducting element has a cable-like or longitudinally extendedconfiguration.
 87. The reflective mirror according to claim 85, whereinthe mirror body has a shape, and the at least one thermally conductingelement has a symmetry characteristic that does not correspond to saidshape.
 88. An optical arrangement, comprising a mount, an opticalelement fastened in the mount, an additional flexible thermal conductorat said optical element.
 89. An optical arrangement according to claim88, wherein said optical element is selected from a group consisting ofmirrors, lenses, prisms and transmitting elements.
 90. An opticalarrangement according to claim 80, wherein said optical element isselected from a group consisting of mirrors, lenses, prisms andtransmitting elements.